Gravity Illusion - Which Ball Falls First?

A fun and intriguing physics experiment that will have people second guessing themselves and eager to see the results of the race. An interesting educational tool to discuss scientific principles such as gravity, acceleration and velocityI. A classic example of the calculus of variations is to find the brachistochrone, defined as that smooth curve joining two points A and B (not underneath one another) along which a particle will slide from A to B under gravity in the fastest possible time.

[minhchaubuingoc]

Now I know which slide to avoid at the water park

[drndroid]

I always thought red was the fastest colour. Thanks Ferrari...now I don't know who to trust.

[flyberd]

I love the ending comment. “Common sense” isn’t the nature of the universe. We don’t innately understand things.

[Bloodywasher]

I'm just a curve playing a curve, disguised as another curve.

[Playingwithproxies]

The blue marble is in near free fall initially and never hits a slope that reduces that initial gain in speed

[Reverend_Salem]

now i want to know if a single cycloid would be faster than the multi one

[jazzdad]

Well, there’s this momentum thing, same height yes, but not same pitch. The steeper pitch starts the ball out faster, so its momentum continues to make it roll taster. In this case, it gains more speed first, then slows a bit, then faster again, but the slow parts don’t reduce the momentum more than it can get back again.

[crisrobinson]

You could make a fortune on this betting in bars like Saul Goodman.

[ryanwalsh]

This makes sense. You could have another ramp where the opposite was the case and it started slow and curved down. It would take longer than the straight ramp. It's about how quickly you can get the ball rolling, literally.

[SteveKilgore]

“Did Bernoulli sleep before he found the curves of quickest descent?”
-most people won’t get this, but if you do, you’re my kinda person

[MrPacman]

I did a science project on this in middle school and got to regional fair lol. Still think it's the coolest physical project I've done

[kregadeth]

For the color blind, the blue ball is on the right side

[mjmorriplymouth]

Another thing about a cycloid. It doesn’t matter where you start the ball rolling on it, it will take the same amount of time to reach the bottom.

[JustARoamer]

I love how you point out incorect intuition! I hate when people try to 'debunk' scientific concepts by saying something along the lines of it doesn't make sense or goes against their intuition. Ive often tried explaing that scientific concepts dont always aling with intuition but no one ever gets it

[FrostNapCat]

That's why the carpet slide in the amusement park of my childhood is formed like this

[blackburngaming]

Because of the initial drop being closer to being straight down, it allows the blue ball to take advantage of more of the 9.8m/s/s of gravity than the red ball can, meaning it gets a faster initial start

[Gehe]

Once you realise what is going on, it makes "common sense" basically with the curves you trade acceleration and distance required to travel. The linear steady slope has least acceleration and least travel. But since acceleration is squared, the more of it you can get the better, as long as your distance needed to accelerate doesn't exceed the time of shortest distance, you win.

Like I said... it makes intuitive sense once you know the rules. After this you can watch things like predatory burds in the sky doing this when they hunt. They glide linear to scout snooth and slow, the do curved slope to plunge in for the strike.

[Ervo]

Interesting, when I was young they taught me that both balls arrive at the same time

[richarddecker]

The right ball accelerates faster because the kinetic energy is released sooner

[meateaw]

Intuitively this makes sense, the ball on the right had a greater acceleration right at the start of the drop. The early acceleration gives it a greater speed at the bottom. The final graph showing 3 balls shows an example where the early acceleration is not enough to overcome the greater distance it travels.